1. Field of the Invention
The present invention relates to seals used in vehicles, such as weather strips, and, more particularly, to procedures and facilities for manufacturing these seals.
2. Description of Related Art
Weather strips are used for sealing automobile passenger compartments to prevent rain, washing water, mud, noise and the like from entering the passenger compartment. Opening trim (OT) weather strips (hereafter referred to as xe2x80x9cOT weather stripsxe2x80x9d) and door weather strips seal a space defined between the doors and the body panels located adjacent to the doors. Door glass run channels seal a space between the door frames and the door glasses moving along the door frames.
A typical OT weather strip includes a U-shaped trim and a tubular seal formed integrally with the trim. The trim is secured to a peripheral flange of a door opening of a body panel. Since the trim is required to have a predetermined degree of strength, the trim is formed by embedding a metal core with ethylene-propylene-diene copolymer (EPDM), solid rubber. The outer side of the trim is covered by a decorating layer formed of, for example, thermoplastic elastomer (TPE). It is also required that the seal has an elastic property at the low-temperature. The sealing is thus formed of EPDM sponge rubber.
FIG. 11 shows a conventional-type procedure for manufacturing the OT weather strip. Specifically, a supplier 106 supplies a plate-like metal core to an EPDM solid rubber extruder 101. The metal core is then embedded by unvulcanized solid rubber and supplied to a first die 102. Meanwhile, an EPDM sponge rubber extruder 100 supplies unvulcanized EPDM sponge rubber to the first die 102. The sponge rubber, together with the solid rubber embedding the metal core, is extruded through the first die 102 and formed as one body, or a workpiece having a predetermined shape. The workpiece including unvulcanized rubber is sent to a microwave heating vulcanizing device (UHF device) 103 in which the workpiece is pre-heated. While the workpiece is passing through the UHF device 103, a foaming agent contained in the EPDM sponge rubber activates and starts foaming the rubber. The workpiece is then sent to an air heating vulcanizing furnace 104. By passing the workpiece through the air heating vulcanizing furnace 104, the EPDM rubber is completely vulcanized. The workpiece including the vulcanized rubber is then cooled in the air.
Meanwhile, olefine type thermoplastic elastomer (TPO) used for forming the decorating layer of the trim is molten in a TPO extruder 105. The molten TPO is shaped like a sheet by second die 107 through extrusion molding. Then, the sheet-like TPO is press-fit on the workpiece by a roller. In this manner, the outer side of the trim is covered by a TPO decorating layer. Subsequently, the workpiece is again cooled in the air and bent such that the trim has a U-shaped cross section. The bent workpiece is then cut in a plurality of pieces by a cutter 108. The cut pieces are arranged in a cavity defined in a metal mold such that the pieces are separate from one another while inclined relative to one another by predetermined angles. EPDM sponge rubber is then injected in the cavity and connects the cut pieces with one another. A complete OT weather strip is thus obtained.
In the above conventional-type procedure, the rubber material and TPO may be shaped as one body through co-extrusion molding, instead of shaping TPO separately. In this case, the second die 107 is unnecessary. However, since the vulcanizing temperature of the rubber is normally 180xc2x0 C. to 220xc2x0 C. TPO is re-molten in a vulcanizing device in which the rubber is vulcanized. The re-molten TPO affects the appearance of the weather strip. Accordingly, as described above, TPO and the rubber must be treated separately before the shaped TPO is press-fit on the vulcanized rubber material.
Furthermore, in the above procedure, the trim formed of vulcanized rubber may be placed in the second die 107. The molten TPO is then arranged on the trim in the second die 107 such that the trim is covered by the decorating layer. However, in this case, it is very difficult to supply the trim to the second die 107 at a predetermined position. As a result, the obtained TPO decorating layer does not have a uniform thickness. In addition, if the molten TPO needs to be provided only to a certain portion of the trim, the structure of the second die 107 becomes extremely complicated. The manufacturing costs of the OT weather strip is thus increased. Therefore, in order to reduce the manufacture costs, a second die 107 with a simple structure is used in the conventional-type procedure. However, if TPO is shaped like a sheet by the second die 107, the sheet-like TPO must be independently press-fit on the workpiece after the rubber vulcanization is completed. This press-fitting step complicates the procedure for manufacturing the OT weather strip. Accordingly, it is necessary to provide a procedure for manufacturing a weather strip capable of reducing costs and of simple performance.
A typical door glass run channel has a bottom wall, a pair of side walls, a pair of support lips, and a pair of lip seals. The support lips and the lip seals extend from the distal ends of the associated side walls. The support lips clamp an edge of a door frame that defines an opening in the door frame for receiving a door glass. Each lip seal comes in contact with an inner side of the door glass facing the passenger compartment or an outer side of the door glass facing the exterior of the vehicle. The lip seals are opposed to each other such that the lip seals guide the door glass to move smoothly along the door frame. When a door glass is closed, the lip seals come in contact with the inner and outer sides of the door glass for sealing the passenger compartment, or preventing rain, washing water, mud, noise and the like from entering the passenger compartment. Most of the door glass run channel is formed of a single type of material, such as EPDM solid rubber and TPO. A polyurethane layer is applied on the surfaces of the lip seals and other portions of the door glass run channel coming in contact with the door glass. The polyurethane resin layer allows the door glass to slide smoothly along the door glass run channel.
FIG. 12 shows a conventional-type procedure for manufacturing the door glass run channel. An EPDM extruder 101 supplies unvulcanized EPDM solid rubber to a die 110. The EPDM solid rubber is then shaped in a predetermined shape by the die 110 through extrusion molding. The shaped rubber is sent to a UHF vulcanizing device 103 and then to an air heating vulcanizing furnace 104 in which the rubber is vulcanized. The rubber is then cooled in the air such that a workpiece of the door glass run channel is obtained.
Next, the workpiece is sent to a polyurethane coating booth 111 in which a solution of polyurethane is applied and coated on the workpiece. The workpiece is then passed through a drying furnace 112 in which solvent contained in the solution is evaporated. Subsequently, the workpiece is sent to a solidifying furnace 113 and solidified in the furnace 113. The workpiece is then cooled and cut in a plurality of pieces by a cutter 108. The cut pieces are arranged in cavity defined in a metal mold such that the pieces are separate from one another and inclined relative to one another by predetermined angles. The pieces are then connected with one another by EPDM solid rubber or TPO injected in the cavity. A complete door glass run channel is thus obtained.
The above procedure includes an independent step of applying a polyurethane coating on the lip seals and another independent step of solidifying the polyurethane. These steps prolong the time required for performing the procedure for manufacturing the door glass run channel. Furthermore, the steps for forming the polyurethane layer complicate the procedure and thus increase the cost for manufacturing the door glass run channel.
Furthermore, since most part of the door glass run channel is formed of EPDM solid rubber, the door glass run channel becomes heavier. Since it is required to provide lighter automobiles, lighter automobile parts need be manufactured. In order to meet this need, for example, the volume of each section in the door glass run channel may be reduced. However, it is difficult to reduce the volume of each section in the door glass run channel without hampering its clamping of the door frame and sealing of the passenger compartment. In addition, if most of the door glass run channel is formed of TPO, the door glass run channel becomes lighter. However, the lip seals of the glass run channel become solidity at a low temperature, thus decreasing its elastic property.
A typical door weather strip includes a base and a hollow seal formed integrally with the base. The base is supported by a retainer fixed on an outer edge of a door frame. The door weather strip is formed of a singe material, such as EPDM rubber and TPO. Normally, the base and the seal are formed of EPDM sponge rubber as one body.
Since the entire door weather strip is formed of EPDM sponge rubber, it is difficult to attach the base to the retainer of the door frame in a stable manner. Thus, the door weather strip may be attached to the door frame by a synthetic resin clamp inserted through a hole defined in the base. In this case, the base may be damaged due to its insufficient rigidity, thus causing the door weather strip to fall from the door frame. However, if the door weather strip is formed of TPO such that the rigidity of the base is increased, the elastic property including permanent compression set of the hollow seal is extremely lowered as compared with a seal formed of sponge rubber. Furthermore, the elastic property of the seal formed of TPO is decreased when exposed to a low temperature. The door weather strip formed of TPO is thus not yet in use.
It is an objective of the present invention to provide a relatively light and inexpensive seal used in a vehicle without degrading the sealing and anti-wear characteristics of the entire seal.
To achieve the foregoing and other objectives and in accordance with the purpose of the present invention, a seal for a vehicle is provided. The vehicle includes an opening of a body and a movable member movably disposed in the opening to selectively close and open the opening. The movable member has an outer edge and the opening is defined by a peripheral inner edge of a flange of the body. The seal is mounted to one of the outer edge of the movable member and the inner edge of the body conforming to each other. The seal has a first portion subject to an elastic deformation when being pressed against one of the movable member and the body. The first portion is made of a vulcanizable rubber. The seal includes a second portion made of a thermoplastic elastomer. The first portion and at least a part of the second portion are integrated by coextrusion. The rubber of the first portion is vulcanized when passing through a vulcanizer.
The present invention is also applied to a method for manufacturing seal for a vehicle. The vehicle has an opening and a movable member movably disposed in the opening to selectively close and open the opening. The movable member has an outer edge and the body has the opening defined by an inner edge of a flange. The seal is attached to one of the outer edge of the movable member and the flange of the body conforming to each other. The seal has a first portion subject to a plastic deformation when being pressed against the movable member or the body. The method includes extruding a rubber for forming the first portion; extruding a thermoplastic elastomer for forming at least a part of a second portion different from the first portion; coextruding the rubber and the thermoplastic elastomer which were formed as one body to a predetermined shape in a single die; and vulcanizing the rubber in a vulcanizer that is heated to a predetermined temperature.